Safety device for electric motors



(No Model.) 2 Sheets-Sheet 1.

- E. THOMSON. SAFETY DEVICE FOR ELECTRIC MOTORS. No. 476,330. Patented June '7, 1892.

W/T/VESSES:

ATTORNEY (-NqModel.) 2 Sheets-Sheet B. THOMSON. SAFETY DEVICE FOR ELECTRIC MOTORS.

Patented June 7, 1892.

Z 72mm :274

ATTORNEY.

I UNITED STATES PATENT OFFICE.

-ELlilU 'lIlOMSON, OFLYNN, MASSACHUSETTS, ASSI GNOR TO 'IHOMSOT HOUSTON ELECTRIC COMPANY, OF CONNECTICUT,

'20 tiallineorsource flnsuch casesasim'p'lefuse the motor, because in mzmy instances durlated efiectof the'current, which-interval and waccumulationlcan I a sensitive conti'olli n g device, responsive to an 'Lynn,in the county ofEssex and State of and otherElectl-ic Apparatus, of which the folelectric motor or other apparatus, is oversomew efect which demands alargecurrent,

Y nor doesauelectromiagnetie cut-off or other safety device, responding immediately toan may result in the destruction of the motor by rent will be cut elf-from the motor.

SAFETY DEVICE FOR SPECEICATION forming art of Letters Patent as. 476,330, dated June '7,

VELECTRIC MOTORS.

Application filed October 16, 1889. Serial in. 327,234. (1T0 model) To all whom it may concern.-

Bait known that I, Eaten THOMSON, a cit izcn of the United States, and a resident of Massachusetts, have'invented a certain new and useful Safety Device for Electric Motors lowing is a specification. I

- My invention relates to apparatns'operated from constant-potential circuits and is desigued to provide-a means whereby such apparatnsimiy be cut oil from cour'iection with the line when the apparatus, whether it be an loaded; or carries: undue current, either throu h undue rnec hariical friction or. from suclfas the disappearance or weakening of the counter electro-"move force inthe'case'of an electric mot'oifed from the constant-pbtenplaced'in the circuit doe's not entirely sufliee,

excess I of current; and; openingtheeircuit to ing 1; e operationflofa motor i'tigma'y be oven.

yet this condition n ot be continued long enough to be a I detriment: to the mach-ine,whereas the salhe'condit-ion o't ex'c'essot currentcom': tinned for fifteen or twenty minutes or more the burning of,its; insulation. v i :My invention' introduces into the'ope'ration of a {use or-other cut-off orother. satety' def vice for motors or-othe'r apparatus fed from a constant-potential;circuit the element of time in addition to the element offiexcess of current, whereby alter a v certain inter-val of overload and the production of an 'accurnuelarrauged in my .i n' proved cut-off tosuit the conditions, the cur- I employ as the first element ofv my invention incl-e15 of current beyond a certain limit, such controlling device beingplaced in the branch from the'co ustant-poteutial main with the device to be protected and being adapted tofcall into action the second clement'ot my delayed or in which the etfects of the abnor mal flow of current as manifested by the controlling device requires to be accumulated invention-namely, a device whose action is for a definite or determinatetime, or,in other I words,'a device delaying the ultimate action for a determinate period of time,- dependout upon the time for which the apparatus maybe subjected to abnormal currentwithout injury, and, thirdly, asafety device,such as a-switch or open circuiting or cut-elf device as the last element of myinvention, said third element beingcontrolled by the action ot' the second element,'or that wherein theaccumulative effects are produced, whereby the motor may be thrown out'bf circuit and saved from injury. 4 r

Very many forms of apparatus may be employed, which may be classed under three elements mentioned. Thus an Ielectro-magnet may be'thefirst element, or a thermo-expansion-device operated by. the circuit; or coils arranged to attract or repel, 0 in fact, any

device such. as would be usedto respoudto or indicate a certain strength of current-passing.

such device, such;as are employed incoa trollers or galvanometers, &c. 1, The secgndelement consists of a cor gradually heats upbyits-resistance ,to the current flowing, and after reachingacertai'n temperature brings byex'pansiomfusion,

or oth'er'such thermic action a switch or the third element into operation. The heating eftect'sot the current might/also be -accumulated by permitting the heat developed-to opina confined chamber of suflicient tension to or shifting of a'support,; or the effects of the i overset or'produce a mechanicalmovement prolonged abnormal current flowiug 'inthe The third element of my inve ution'inay be a switch released'b'y adetent,'or a fuse ini'the I coilor portion ofnlelectric circuit thrown .into cir'; 'cui byvth firstelement when'it acts, which 'branch through the motor might-be accumu- 5 lated in any other desired manner, the appa? 'ratus being ,so set-or adjusted that the pro- .longatiou should be a definite one, or one ex- I tended for some period somewhatless than that for which the apparatus may undergo the effect of the current without injury.

too

it a

circuit of the motor brought into a melting colltllllfill by the heat imparted to itin conscuncut-e of the action of the second device or element, in faeta cutoff device giving the properties of an electric switch or other protective device for preventing injury to the motor by excessive current andnndcr the control of the second element of my inventmn. A

In the accompanying drawings, Figure l is a side view of an apparatus embodying my invention. Fig. 2 shows in side view a modification thcrcofgFig. 2-3, one of a number of equivalent arrangements. Fig. 4 shows a modification of the invention. Fig. 5 is a diagram of the circuits, Fig. 1.

II. will be understood that numerous modi- 'lications may be made in the devices used and their arrangement; but my invention is not in reality limited in auyseuse, but includes the elements mentioned and theirsubstantial equivalents combined and adjusted as hereiudescribod.

In' Fig. 1 the clcctro-responsive device is shown-at M as an clectro-magnet whosearmaturo'N is mounted on an armature-lever and is pulled against a' retractilejspring S, which may be made adjustable. ver carries a Contact at K, which on the dcscent of the lever is brought'against the pillar l, the back-stop Z being insulated.

F is a f use-wire mountcd'between two pil- .l.-us or supports V V and connecting such supports electrically. 'lho supports V V for the fuse-wire are of metal and wound around with coils C C, but insulated therefrom. The coils C C are arranged to be thrown'into circuit upon the completion of the contact-at K,

and the current which then passes is sufiicient to produce considerable heatnvhich heat is conducted to the parts V X, which the coils surround and which parts are made preferably of copper or good conductor of heat, the heat being carried from the coils to the fuse-wire F, so as to provoke its melting when the contact K is closed.

t symbolizes an electric motor. The magnet M and armature are adjusted so as not to act. in closing contact until an ahnornutl current traverses the motor G from the constant; potential or other line whose feeding wires or mains are re'ircscnted by the letters a I The apparatustis connected from the wire a to the fuseavlro post Vf, connection from such post being continued by the fusewirc itself to the other v. Connection is taken'froni Y to oint'terminal of the coils on the magnet N, the other connection or terminal being madoto *ihoi pillar .1", where it is shown attached to t ie wirc leading from'the motor G, the other terminal of the motor being connected, as shown, to the main or feeding wire b. The wire coils C C, which are made of line wire, nay be connected in shunt from a to I: through the contact K when closed, as follows: from line I: to t) arma- -ture-lever whichcarries the armature N, and

The armature-leupper contact K, post 1', and .tdi'abjnay-of coil M and fuse F. All parts of the apparatus are suitably insulated to prevent the elvist} 7t ence of other circuits than "those. niontionedf It will be seen that the fuse F- i; in serics'with the motor G. The fuse B is adjusted t o-melt at. once when a very excessive current flows 1 through the motor G, bnt'will not. melt. for};

gradually heat the coppercor es'ot thc coils 85 C C, and which heat finally reaches tn-amount;

which, in addition to that. alrcady'prgduoed inthe use F by the current. flowing through it, causes the melting of the fusoia'nd t-hcfupture of the circuit through tho. m'otor G.';-;Thc' three 0 element's are then, first, the rcspo nsivoclectroe magnet. M, acting our-an overload, which'mugnot controls the second -;ele mentf pr heziting-g coils C C, which introduces a timo'Jactor for l the completion of the actions, and, ti'nallyJho 95- third element, called into. action by{ .tlte;oporation of the second element, as the fuse-wire F, which is acircuit'- rupturing device or. switch. 7 Instead of the magnet M any othocdo'vlco IOO responsive to the action of electric current may he used. -'lhi1s, for instauce,an-oxpansible wire M Fig.- 3, maybe arranged so that when heated by an undue current passing through it. or otherwise affecting it it. will expand and closca contact at K byallowing'thb contact-lever L to drop' from the position shown. The contact at K, as before, controls the current admitted to the tine wire coils U C',and the fuse'F,-as before, is caused to melt on the continuance of an abnormal load fora time sufficient to produce damage. v 7 'lho devieos,Figs. 1 and 2, in case'the ove r: load does not exist or a sufficient time-to provoice the melting of the fuse F and the ruptnre of the circuit, will r -establish thoorigL nal conditions by the opening of the contact K on the release of the armature N,as in Fig. I, when the normal current flows in M, or by the contraction of the wire M, Fig. 2. Of course itis not necessar that the coils C C be in'circni as shown. They may bethrown into circuit in anyother way and be fed from any source of current. In Fig. 3 they are shown as led from the main circuit, kept shunted hy'a' tiontact K, ulitil by our pull onihc armature J, due toexcessive currcnt,'as in Fig. 1, such contact His opened, when the current; at once traverses the cells C C and warms them gradually and finally to the to uired degree when the ad jnstmonts have been properly made. Q

Fig. 1 shows an equivalent subs-ti nteior the coils t C, arranged to heat and orn'rthethe expansion of cut-off F. The dcvicc, -Fig. 4, depends upon veloped by an electric current, which, being allowed toactfor a sullicient time by the eleclheweightot the liquid will tilta lever. Bulb B contains heating-coil H, whose circuit iscoutrolled by M. Qn cloureof contact K thefluid will'be gradually driven over to one sideas the coil beats and vaporizes the sameand the vapor under tension accumulates in the chamber at the left of the figure until finally the balance is overcome and the whole pivoted-receptacle will be thrown over from'the position shown to a-position in which the right side-of the structure is the lower. On the movement ot the bulbs B B around the pivot on which they are suspended they may be made to throw a. detent D from under-the switch-10+ ver A, whereby it may break contact at R. The switch-contacts R con trol'the flow of current to the motor G, and when open .cut oflf the supply. They are in series with the motor G and magnet M.. This'device is .similar in operation to that of Figs, 1 and 2. 'A heating or expansion of fluid takes placeinstead otthe effect on the coils C C, which causes the opening of a cut-off, such as switch R, instead of the operation 'of a cut-off, such as 81 fuse F, which is melted, as in Fig. 1. action will be readily understood from an inspection of the figure.

What I claim as my invention is' l. f lhc combination, with a constant-potential circuit, of a normally-closed branch therein, a translating device, and aprotective device included in said branch, said protective device being responsive to abnormal current and being adjusted or constructed to' open said branch cireuitonl y aftera predetermined time, dependent upon and within the period for which the translating device may carry the abnormal current without injury.

2. -,'lhc combination, with a translating device in a branch from a constant-potential circuit, of an automatic circuit-interrupter in said branch responsive to abnormal currents therein, a derived circuit around said translating device assisting said circuit inlet-- ruptcr, and an clcctro-rcspousive device in said branch circuit responsive to abnormal current for controlling said derived circuit.

3. The combinatiomwithamotor inabranch from constantpotcntial-mains,of acircuit-intcrrupter in said branch responsive to abnormal currents therein, a derived circuit for govcrning the operation of said circuit-interrupter, and an clectro-responsive device in said brszv'ih controlling said derived circuit.

The

4. The combination, with acoustantpotcntial main, of a'brauch containing a translating device,and a protector in said branch dependent for its action upon the accumulated 7c eliects of abnormal current prolonged in said branch beyond the, period of the usual or ordinary fluctuations of current that it prolonged wouid injure the apparatus.

5. 'The combination, with an electric appa- '7 5 Y raius fe froma source of potential suificient todamagc thesame, of an electro-responsive device adjusted to respond to excess of current in the said apparatus, a cut-elf or protective switch for such apparatus, and a (10- vice responsive to the accumulated efiects oi the current,- as described, and governed bysuch electr -responsive deviceaud adapted :to bring the cut-off into operation on a predc termined lapse of time, determined or lim ted 85 by the period'during which the apparatus may be subjected-to .thesame excess of current withoutdamage from heating.

6.. The combination, with an electric appa- V ratus, of a. safety cutout, an electro respons- 9o ive device connected to thecircuits of the apparatu's and adjusted to respond to abnormalcurrent strengths, and an electric heataccumulat'or in which .the heating effects of an electric current are absorbed era'ccum ulatcd',

as described, said heater being controlled by the electro-responsive device and being adjusted, as described, to bring the cut-off into operation onlyafteri the closure of. circuit through the heaterhas been made for a pro- Ioc longed period,'determined by the time during. which an abnormal current. may flow Without" injury to the apparatus.

'l. The coxnbination,with an electric safety fuse of conducting'mate'ri'ahot an-electrlc'ros heater, to the heat-radiating effects of which responsive device governing the circuit of the' r r 5 heater and responsive to excessive current-in the circuit of the fuse. c

U. The combination, with the electric heating-coils,of asafety-iuse consisting of apiece of fusiblcconducting materialincluded in an no electric circuit and mounted on a hcat-conducting support subjected to the heating tion of said coils, as and for the purpose described.

Signed at Lyun,in'the county of Essex and :25

State of Massachusetts, this 8th day of 0cto bcr, A. D. 1889.

ELIlIU TI IOMSON.

Witnesses: Jiwuscur Gmnonev, A. L. Rov 

